1. Field of the Invention
The present invention relates to work vehicles such as agricultural work vehicles, and, more particularly, to steering systems within such work vehicles.
2. Description of the Related Art
Work vehicles typically include agricultural, construction, industrial and forestry work vehicles. Examples of work vehicles include agricultural harvesters and tractors, construction backhoes, and forestry feller/bunchers.
An agricultural harvester known as a “combine” is historically termed such because it combines multiple harvesting functions with a single harvesting unit, such as picking, threshing, separating and cleaning. A combine includes a header which removes the crop from a field, and a feeder housing which transports the crop matter into a threshing rotor. The threshing rotor rotates within a perforated housing, which may be in the form of adjustable concaves, and performs a threshing operation on the crop to remove the grain. Once the grain is threshed it falls through perforations in the concaves onto a grain pan. From the grain pan the grain is cleaned using a cleaning system, and is then transported to a grain tank onboard the combine. The cleaning system includes a cleaning fan which blows air through oscillating sieves to discharge chaff and other debris toward the rear of the combine. Non-grain crop material such as straw from the threshing section proceeds through a straw chopper and out the rear of the combine. When the grain tank becomes full, the combine is positioned adjacent a vehicle into which the grain is to be unloaded, such as a semi-trailer, gravity box, straight truck, or the like; and an unloading system on the combine is actuated to transfer the grain into the vehicle.
Combines, as well as other agricultural vehicles, have tended to be larger over time since farming operations have become larger over time. With power steering systems it is still possible for an operator to easily steer these large combines. However, some geographic regions in the world (e.g., Europe) have regulated requirements regarding the ability to steer a combine when the power steering system is not powered. With the power to the power steering off, it can be very difficult for an operator to steer the heavy combine with high forces between the ground and wheels.
What is needed in the art is a work vehicle which can be satisfactorily steered when the power steering system is not powered.